He left homeland wandering — must be a nut (6)
I believe the answer is:
almond
'a nut' is the definition.
(almond is a kind of nut)
'he left homeland wandering' is the wordplay.
'left' is a deletion indicator.
'wandering' is an anagram indicator.
'homeland' with 'he' taken out is 'omland'.
'omland' anagrammed gives 'ALMOND'.
'must be' acts as a link.
(Other definitions for almond that I've seen before include "Nut (tree)" , "Nut which provides cake icing" , "Nutlike seed" , "Nut-like kernel" , "Oval-shaped nut" .)